CH5: Alcohols from Carbonyl Compounds: Oxidation-Reduction and Organometallic Compounds Flashcards
Types of carbonyl groups
1) C.A.
2) Ester
3) Aldehyde
4) Ketone
C.A. reduction
Reduce to a primary alcohol
Need LAH in ether soln followed by H2O and acid
LAH
Strong reducing, reduces everything
Needs -78 to 0 degrees
NaBH4
Weak reducing, only ketones and aldehydes
Ester reduction
Reduced to a primary alcohol
1) LAH, Ether
2) H2O, H2SO4
OR
1) High pressure, heat, and H source (hydrogenation at a high pressure)
Aldehyde + Ketone reduction
Primary alcohol and secondary alcohol
Reduced with LAH or NABH4, NaOH
What do reducing agents do
Provide a hydride source (H-) to act as a nucleophile on a pi bond
Primary alcohol oxidation
KMnO4 can oxidize all the way to C.A. it is strong
Use PCC to stop at the aldehyde stage
KMnO4
Strong oxidizing agent takes primary alcohols to C.A.
1) KMnO4, OH-/H2O 2) H3O+
PCC
Stops oxidation of primary alcohols at the aldehyde stage, it is used in organic solvents ex. CH2Cl2 and heat
Ketone oxidation
1) Chromic acid: H2CrO4 in acetone with heat
OR
2) Jones reagent: CrO3 in acetone with heat
Chromic acid/Jones regant
Form ketones from secondary alcohols
Aldehydes in water form________
Hydrates, if we use H2CrO4 after it can then be attacked to form a D.B.
A bond is ______reactive the more ionic it is
More
Organometallic compounds
C-Metal bonds hence organo (carbon) metallic (metal), can turn carbon into a nucleophile instead of an electrohile because the metal is super positive
Organolithium reagants
React an alkyl halide with 2Li in ether solution
R-Li and Li-X form
Reactivity-Use I or Br only
Gringard reagents
Mg and an alkyl halide in ether solution produces this
What is important when dealing with organolithium + grignard reagents
They are super basic and will remove an H from alcohols, water, any H attached to N, O or S.
They must be used in anhydrous (no hydrogen soln)
Alkynides
Organometallic reagants are great for creating a CT.B.N nucleophile. These compounds are great nucleophile and can add carbon-carbon bonds
Grignard + oxiranes (epoxides)
This leads to ring opening at the least substituted carbon and forms a C-C bond 2 carbons down from the alcohol’s hydroxyl group. H3O+ is used at the end
Primary alcohol from grignard and ketone/aldehyde
The grignard attacks the carbon forming an alkoxide. This is then protonated by acid, yielding a 1, 2, or 3 alcohol
Formaldehyde + Grig
Aldehyde + Grig
Ketone + Grig
1, 2, 3 ALCOHOLS…always bumps up one because r group is added to the carbonyl carbon
Sodium alkynides (NaNH2)
Create nucleophiles, especially for C tb C with an acidic H
Tertiary alcohol from ester
2 moles of grignard reagent followed by NH4Cl/H2O yields a tert alcohol
-OR is the first L.G.
